var dragObj;
var scrollObj;
// Determine browser and version.

function Browser() {

  var ua, s, i;

  this.isIE    = false;
  this.isNS    = false;
  this.version = null;

  ua = navigator.userAgent;

  s = "MSIE";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isIE = true;
    this.version = parseFloat(ua.substr(i + s.length));
    return;
  }

  s = "Netscape6/";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isNS = true;
    this.version = parseFloat(ua.substr(i + s.length));
    return;
  }

  // Treat any other "Gecko" browser as NS 6.1.
  s = "Gecko";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isNS = true;
    this.version = 6.1;
    return;
  }
}

var browser = new Browser();

function dragStart(event,id) {

  var x, y;
  if (id) dragObj = document.getElementById(id);
  else {
    if (browser.isIE)
      dragObj = window.event.srcElement;
    if (browser.isNS)
      dragObj = event.target;
  }

  // Get cursor position with respect to the page.
  if (browser.isIE) {
    x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
    y = window.event.clientY + document.documentElement.scrollTop  + document.body.scrollTop;
  }
  if (browser.isNS) {
    x = event.clientX + window.scrollX;
    y = event.clientY + window.scrollY;
  }

  // Save starting positions of cursor and element.
  dragObj.cursorStartX = x;
  dragObj.cursorStartY = y;
  dragObj.elStartLeft  = parseInt(dragObj.style.left, 10);
  dragObj.elStartTop   = parseInt(dragObj.style.top,  10);

  if (isNaN(dragObj.elStartLeft)) dragObj.elStartLeft = 0;
  if (isNaN(dragObj.elStartTop))  dragObj.elStartTop  = 0;

  // Capture mousemove and mouseup events on the page.

  if (browser.isIE) {
    document.attachEvent("onmousemove", dragGo);
    document.attachEvent("onmouseup",   dragStop);
    window.event.cancelBubble = true;
    window.event.returnValue = false;
  }
  if (browser.isNS) {
    document.addEventListener("mousemove", dragGo,   true);
    document.addEventListener("mouseup",   dragStop, true);
    event.preventDefault();
  }
}


function dragGo(event) {

	var x, y;
	// Get cursor position with respect to the page.
	if (browser.isIE) {
		x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
		y = window.event.clientY + document.documentElement.scrollTop  + document.body.scrollTop;
	}
	if (browser.isNS) {
		x = event.clientX + window.scrollX;
		y = event.clientY + window.scrollY;
	}
      var vlim = parseInt(dragObj.parentNode.style.height)-parseInt(dragObj.style.height);
	var  posY = dragObj.elStartTop  + y - dragObj.cursorStartY;
      if (posY<0) posY=0;
    	else if (vlim!="undefined"&&posY>vlim) posY = vlim;
	// Move drag element by the same amount the cursor has moved
	dragObj.style.top  = posY + "px";
	// since we are not concermed with horizontal movement left is ALWAYS 0px;
	// this is the scrolling content window
      if (scrollObj!="undefined")
	{
            var contentHeight = scrollObj.offsetHeight;
		var scrollLimit = contentHeight-parseInt(scrollObj.parentNode.style.height);
		var vPercent = posY/vlim;// alert(vPercent);
            var scrollY = scrollLimit*vPercent;
		if (scrollY<0) scrollY=0;
		scrollObj.style.top = Math.round(scrollY*-1)+"px"; // will always be a negative value
	}
 	//
	  if (browser.isIE) {
	    window.event.cancelBubble = true;
	    window.event.returnValue = false;
	  }
	  if (browser.isNS)
	    event.preventDefault();
}

function dragStop(event) {

  // Stop capturing mousemove and mouseup events.

  if (browser.isIE) {
    document.detachEvent("onmousemove", dragGo);
    document.detachEvent("onmouseup",   dragStop);
  }
  if (browser.isNS) {
    document.removeEventListener("mousemove", dragGo,   true);
    document.removeEventListener("mouseup",   dragStop, true);
  }
}